This is a project I made that sums prices of specific catagories together.
You can see a live version here:
http://experiments.andreit.me/roboPrice/roboPrice.php
The hardest thing about this project was actually the front end. I am not used to how web front ends work at all, so all the back end data-wrangling in PHP took less than an hour, while figuring out a "decent" front end was the hard part for me.
Hope that you like it!